This invention relates to the field of heating presses that enable producing sheet metal parts intended for aeronautical material or other, by supraplastic deformation at temperatures close to 1 000xc2x0 C. and using appropriate tooling.
The invention relates, on these presses, to the arrangement of the sliding plate on which is attached the lid of the forming tools, and more especially, the hooking system of such lid.
The sliding plate consists of a single water-cooled metal plate, integral with the working actuator(s), and of a heating ceramic plate interposed between the metal plate and the tooling lid.
This ceramic plate is composed of blocks that are fixed to the metal plate by appropriate tension rods. The blocks making up the plate are made of material such as vitreous silica.
This ceramic plate acts as a heating plate and has numerous advantages associated with its dimensional stability regardless of the temperature, its surface evenness, its low thermal inertia and its low maintenance cost.
The tools, and in particular the lid, are heated using heating elements such as resistive wires or heating pipes. These heating elements are inserted in holes provided in the ceramic blocks, close to the surface that is in contact with the top of the lid.
These heating elements are multiple, spread over one or several layers and form a compact network so that the lid of the forming tooling, on the sliding plate, is fixed generally using a hooking system arranged on the upper lateral edges of the lid, co-operating with the rims of the sliding plate.
This lateral hooking system has several drawbacks. It requires adaptation of the geometry of the tooling lid and, moreover, it enhances deformation of the said lid.
This invention provides a hooking system that enables to obviate these drawbacks thanks to a peculiar arrangement of the sliding plate.
The invention provides a hooking system for a tooling lid onto the sliding plate of a hot forming press, which sliding plate comprises a water-cooled upper metal plate and, below the latter, a ceramic plate provided with heating elements that enable to reach a temperature in the order of 1 000xc2x0 C., which hooking system comprises rails made of refractory steel that are inserted in grooves in the said ceramic plate, which rails enable on the one hand to fix the said ceramic plate below the said metal plate via tension rods provided between the rails and the metal plate and, on the other hand, to hook the said lid, for example using H-section parts that nest into T-shaped grooves provided opposite to one another in the said rails and the said lid.
Still according to the invention, the thickness of the hooking rails is smaller than the depth of their reception grooves, in order to avoid any contact between the said rails and the top of the lid.
According to another embodiment of the invention, each rail is fixed to the upper metal plate via tension rods made on the one hand, of a refractory steel rod provided at its lower end with a head inserted in an appropriate cavity of the rail that is located above the T-shaped groove, and at its upper end, with a nut, and on the other hand, between the said nut and the top of the metal plate, with compensation means comprising a spring and/or a stack of single-coil spring lock washers.
According to another embodiment of the invention, the length of the rails is limited and should not exceed twice the distance between two adjacent tension rods that enable fastening them, in order to limit the problems associated with deformation by elongation of the said rails when subjected to high temperature.
According to another embodiment of the invention, when in the same groove, the rail consists of several rail sections, the ends of both sections of adjacent rails comprise a male/female arrangement to enable their nesting into one another, thereby providing continuity at, particularly, the T-shaped groove and enabling feeding H-section parts through without any problems.
According to another embodiment of the invention, in order to obtain good thermal distribution, heating elements are placed also close to the bottom of the reception groove of the rails, on either side of the tension rods, for some continuity of the heated surface.
According to another embodiment of the invention, in order to keep the same thermal inertia with respect to a conventional ceramic plate, the thickness of the ceramic plate with grooves, is increased with the thickness of the fastening rails.
According to another embodiment of the invention, the width of each reception groove of the rails is greater than that of the rails, whereas the said rails rest solely at the bottom of the said groove, which bottom is connected to the walls of the said groove by roundings in order to avoid initial and potential fractures.